Aromatic amine derivatives are used for ballast groups on photographic couplers, and also useful as intermediates in the syntheses of various functional compounds.
A known method of synthesizing such aromatic amine derivatives is shown below as Route (1), wherein a Lossen rearrangement is utilized (as presented, e.g., by Y. H. Yale et al. in Chem. Rev., vol. 33, p. 209 (1943)). ##STR1##
In the above formulae, R and R' each represents an alkyl group or an aryl group.
In the Lossen rearrangement reaction, it is generally necessary in order for the reaction to proceed smoothly, that the reaction take place under relatively mild conditions, and that the hydroxyl group of hydroxamic acid be changed in advance to a desirable splitting-off group (e.g., by acylation) before undergoing the reaction under basic condition (as reported, e.g., by W. B. Renfrow et al. in J. Am. Chem. Soc., vol. 59, p. 2308 (1937), by M. A. Stolberg et al. in ibid., vol. 77, p. 765 (1955), and by R. Swidler et. al. in ibid., vol. 78, p. 3594 (1956)).
On the other hand, it is known that the rearrangement can proceed without a previous acylation of hydroxamic acid when heating is carried out in the presence of an acid catalyst such as polyphosphoric acid. Specifically, the reaction requires a high temperature of about 160.degree. C. (as reported, e.g., by H. R. Snyder et al. in J. Am. Chem. Soc., vol, 75, p. 2014 (1953)).
Also, attempts to omit the process of acylating hydroxamic acid under mild conditions were made by D. G. Hoare et al. and S. Bittner et al. Specifically, D. G. Hoare et al. reported that the reaction proceeded smoothly at room temperature by adding excess 1-benzyl-3-dimethyl-aminopropylcarbodiimide to a weakly acidified aqueous solution containing hydroxamic acid (J. Am. Chem. Soc., vol. 90, p. 1638 (1968)). S. Bittner et al. reported that the reaction proceeded smoothly at room temperature under neutral condition by adding triphenylphosphine and diethylazodicarboxylate in amounts equimolar with hydroxamic acid (Tetrahedron Letters, vol. 23, p. 1965 (1974)).
The foregoing method which comprises heating hydroxamic acid in the presence of an acid catalyst such as polyphosphoric acid can avoid an acylation process step, but has the drawback that a high temperature of about 160.degree. C. is required for the reaction to proceed, and the acid catalyst polyphosphoric acid is difficult to handle due to its high viscosity.
Using to the methods proposed by D. G. Hoare et al. and S. Bittner et al., the intended compounds can be obtained under mild conditions while avoiding an acylation process step. However, such methods cannot necessarily be said to ensure a cheap production of the designed compounds, considering the price and type of reagents used.
Therefore, it is desirable that a method be provided for producing aromatic amine derivatives in a high yield from generally inexpensive reagents, under mild conditions without needing an acylation step.